Thermodynamic quantities will be obtained for the transfer of ribonuclease A, lysozyme, chymotrypsin, and cytochrome C and their reduced alkylated derivatives from dilute buffer to various cosolute solutions. The cosolutes include guanidinium chloride and ethanol. Similar data will be obtained for a variety of model substances including amino acids and amides. These model substances will be chosen such that they will provide a set of thermodynamic quantities of transfer for each of the amino acid side chains and the peptide backbone unit from buffer to cosolute solutions. Using values of the accessibility of the various groups of a protein determined by computer analysis of the known crystal structure, it will be possible to calculate the transfer quantities for the whole protein. Comparison of this value with the experimental quantity will allow an experimental test of the quality of computer modeling of the protein surface.